TB thrives in crowded houses

Sydney, Aug 11 (IANS) Research based on census data and notified tuberculosis cases over a five-year period has shown that it thrives in crowded houses. The University of Otago (Wellington) study, comprising 1,898 cases between 2000 and 2005, found that TB is still an important infectious disease.

TB affects a third of the world population, 10 percent of whom will progress to active disease. Its impact is further worsened by the HIV epidemic and rising levels of drug resistance.

“While the focus of TB control is on prompt case detection and effective treatment, better housing conditions and reduced levels of crowding also have a role in controlling the spread of this disease,” said study co-author Michael Baker.

This is the first published study in New Zealand or Australia to examine the effects of household crowding on TB, while controlling for other important risk factors for this disease.

“Unlike some previous studies, we were able to control for the effects of known risk factors, notably poverty and migration from high incidence countries. Linking to census data also allowed us to include a relatively large number of cases,” said Baker.

The study, which focussed on the the under-40 population, found that every one percent increase in average household crowding caused an eight percent increase in the expected TB count, assuming other variables were constant.

People living in the most crowded quintile (20 percent) of neighbourhoods would expect to have a TB risk approximately 70 percent higher than those living in the least crowded quintile.

“The finding that TB rates are associated with crowded living conditions fits with what we know about the transmission of this bacteria via small airborne droplets,” said Baker. “Household crowding increases opportunities for active cases to infect other household members, particularly children.”

These findings have been published in the Journal of Epidemiology and Community Health.